Exemplary embodiments of the invention relate to a technique for restraining temperature rise in a light exiting-side polarizer constituting a liquid crystal light valve in a projector.
The related art includes a liquid crystal light valve that is used as an electro-optical device of a projector that projects an image.
This liquid crystal light valve includes a transmission liquid crystal panel, a light incident-side polarizer provided on a light incident surface side of this liquid crystal panel, and a light exiting-side polarizer provided on a light exiting surface side. In the liquid crystal panel, the direction of polarization of polarized light exiting from the light incident-side polarizer is modulated in accordance with a driving voltage applied to each pixel according to an image signal. Of the light modulated in the liquid crystal panel, only the light having a direction of polarization coincident with the polarization axis of the light exiting-side polarizer is caused to exit from the light exiting-side polarizer. The other light is absorbed by the light exiting-side polarizer. Thus, the liquid crystal light valve modulates incident light in accordance with the image signal.
Therefore, in the liquid crystal panel, the light incident-side polarizer and the light exiting-side polarizer constituting the liquid crystal light valve, there is a loss in exiting light with respect to incident light and this loss causes heating and temperature rise. Particularly, in the light exiting-side polarizer, the temperature rises at a higher degree because it absorbs a large quantity of light. The temperature rise in the light incident-side polarizer is relatively low because the light incident on the light incident-side polarizer is usually light polarized in the direction of polarization that is the same as the polarization axis of the light incident-side polarizer in consideration of efficiency.
In a related art projector, a liquid crystal light valve is cooled by blowing from a cooling fan, and the number of rotations of the cooling fan is controlled so that the temperature near the liquid crystal light valve can be maintained within a predetermined range of temperature specification, or the quantity of light emission of a light source is controlled so that temperature rise in a light exiting-side polarizer and a liquid crystal panel is restrained. See, for example, related art document JP-A-2000-194072.
Alternatively, in another related art projector, a power supply to a light source that generates illuminating light is shut down when the temperature of a light exiting-side polarizer becomes abnormal. Accordingly, temperature rise in the light exiting-side polarizer and a liquid crystal panel is restrained. See, for example, related art document JP-A-2003-43440.